It turns out that there's an easy way to make this heat transfer much
more efficient. If, as soon as air molecules are heated up, they are
somehow knocked away from the metal surface, then other air molecules
can be heated. (Otherwise, the first heated molecules effectively
'insulate' the other air from being heated by being in the way.The easiest way of doing this is to use a suitable blower to blow the heated air molecules away.
This is referred to as forced convection, or in the case of air, forced air convection. All high efficiency air heating systems use some sort of forced air convection.